The invention is directed, broadly, to those breakerless ignition systems requiring an annular interrupter array irrespective of whether the pulse generating circuit is optically or magnetically controlled. Exemplary breakerless systems of the type contemplated are disclosed in U.S. Pat. Nos. 3,792,261; 3,822,686; and 3,861,370. The invention is more specifically concerned with the conversion of conventional distributors employing cam operated breaker assemblies to breakerless distributors.
Breakerless control mechanisms normally employ a housing structure defining a discrete, arcuate air gap through which an annular interrupter array is rotated at a speed proportional to engine speed. The housing structure, containing the optical or magnetic components as the case may be which are modulated by the passage of the interrupter array through the air gap, is conventionally integrated with the vacuum advance plate via the preformed breaker assembly and/or condenser mounting apertures therein while the conventional interrupter array is mounted for rotation with the distributor drive shaft. The criticality of close tolerance positioning of these coacting control means has previously dictated either a specifically designed breakerless distributor assembly or expensive adaptations for retrofit of conventional distributors. The latter primarily for the reason that advantage has not been taken of locator mountings preformed for the annular interrupter array on an already precision distributor part as is conventional practice in the integration of the coacting housing structure with preformed mounting apertures in the vacuum advance plate. Stated differently, although a standardized housing structure defining the air gap portion of the control system may be reproducibly located on a given conventional distributor model via the preformed mounting apertures in a precision located part, i.e. the vacuum advance plate; the interrupter array has not previously been so located, radially of the axis of rotation, with respect to an already precision mounted part. Rather, previous interrupter arrays have been interconnected with the drive shaft by various means such as a shaft secured retrofit plate assembly or a press fit with the drive shaft or breaker cam. The close tolerance machining and assembly procedures required to assure concentric rotation of the interrupter elements taken with the necessity for stocking different interrupter configurations for retrofitting a common distributor model to accommodate engines having different numbers of cylinders are primarily responsible for the aforesaid "expensive adaptations".